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GCOS Essential Climate Variables (ECV) Salinity: A measure of the quantity of dissolved salts in seawater. It is formally defined as the total amount of dissolved solids in seawater in parts per thousand (0/00) by weight when all the carbonate has been converted to oxide, the bromide and iodide to chloride, and all organic matter is completely oxidized. These qualifications result from the chemical difficulty in drying the salts in seawater. In practice, salinity is not determined directly but is computed from chlorinity, electrical conductivity, refractive index, or some other property with a relationship to salinity that is well established. The relationship between chlorinity Cl and salinity S as set forth in Knudsen's tables is S=0.03 + 1.805 CL. In 1940, however, a better expression for the relationship between total dissolved salts Σ and chlorinity was found to be Σ=0.07 + 1.811 CL. In more recent times, with the advent of devices that measure continuous records of conductivity electronically (e.g., CTD or conductivity–temperature–depth profiler), a new “practical salinity scale” has been determined. It is defined in terms of its electrical conductivity relative to a prescribed standard and it is given the units psu, for “practical salinity units.” For most purposes one can assume that the new unit, psu, and the older unit, 0/00, are synonymous. (From the Glossary of Meteorology) A defining characteristic of ocean water is its relatively high concentration of dissolved salts or salinity. Understanding why the sea is salty begins with knowing how water cycles among its physical states: liquid, vapor, and ice. As a liquid, water dissolves rocks and sediments, and reacts with emissions from volcanoes and hydrothermal vents: this creates a complex solution of mineral salts in our ocean basins. In other parts of the cycle, however, water and salt are incompatible: water vapor and ice are essentially salt free. More...(from the NASA Goddard Space Flight Center web site) [ECV Matrix Main Page] [About the ECV Matrix] [Reference Documents] [Contact] [Updated July 28, 2010]
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